Author Topic: Why?  (Read 15793 times)

Offline zedrein

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Why?
« on: January 23, 2009, 09:45:32 am »
As in, why do many game consoles even output RGB in North America? I can perfectly understand why in Europe the SNES, Genesis, PS1 and others would have 15kHz RGB output, but considering that in the US, we don't have tv's that natively support that format why would console manufactures even include it as an option?

Offline kendrick

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Re: Why?
« Reply #1 on: January 23, 2009, 11:15:15 am »
Uniformity. For many game consoles, the only difference among regions is a jumper or a ROM chip. When designing a fabrication and manufacturing process that needs to be as fast and as consistent as possible, it doesn't make sense to remove capabilities unless you save a lot of money by doing so. If every console has the same encoder chip and the same video connector, then you don't have to worry about different machines having different capabilities if all you need to do is drop in a trace and ship it to the right region.

I remember that Dreamcasts were manufactured with this in mind. When the US region started running out of consoles, JPN-region machines were retooled and repackaged to meet demand. There's every advantage to leaving RGB in American consoles, and very few disadvantages.

Offline Endymion

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Re: Why?
« Reply #2 on: January 24, 2009, 08:01:33 am »
ALL consoles work in RGB because this is the first step that leads to ALL of the other formats. The only thing that is happening when RGB is in use, instead of composite or s-video or what have you, is that direct link, simple as that. So it would be kind of stupid to make some special console just for the USA that does not function with RGB, when it would be used/needed/requested in other world region televisions. By having just one product you can make simple changes which will effect regional marketing purposes, but you can maintain one assemblage, less waste and expense.

Offline kendrick

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Re: Why?
« Reply #3 on: January 24, 2009, 08:40:26 am »
Endymion is right, of course. It's worth mentioning that there are exceptions too. The Atari 2600 generates luma and chroma natively, and doesn't produce any sort of RGB signal that can be tapped, to name just one example.

Offline ken_cinder

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Re: Why?
« Reply #4 on: January 24, 2009, 10:39:21 am »
What's up with the SNES Jr. and the later models of N64 then? From what I've read from you guys and on the wiki, you can't get RGB out of them, but earlier models you can.

Online Link83

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Re: Why?
« Reply #5 on: January 24, 2009, 12:20:39 pm »
What's up with the SNES Jr. and the later models of N64 then? From what I've read from you guys and on the wiki, you can't get RGB out of them, but earlier models you can.

With the SNES Jr the video chip is still capable of RGB, its just that it isnt connected up (to reduce costs even further I assume, or just to make it easier to reduce the motherboard size)

Early N64's have the the Video DAC and the Video Encoder separately so are easier to RGB mod as we can tap the RGB before its encoded, Both chips were eventually combined together into one chip in later N64's to reduce costs. The chip still decodes into RGB internally before encoding it into Composite/S-Video, but its all internal so there isnt any way for you to tap into it anymore.

Unless you meant why didnt they output RGB to begin with? In which case I would say its just a matter of Nintendo being stingy with their video modes - something they have a nasty habit of doing  :(
« Last Edit: January 24, 2009, 12:22:48 pm by Link83 »

Offline ken_cinder

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Re: Why?
« Reply #6 on: January 24, 2009, 12:58:58 pm »
No, I was under the impression getting RGB out of them was impossible.

So you could tap RGB from the SNES Jr. right off the VDP?

I don't even know why I ask about things I'll never bother with. Call me curious I suppose.

Online Link83

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Re: Why?
« Reply #7 on: January 24, 2009, 03:05:36 pm »
No, I was under the impression getting RGB out of them was impossible.

So you could tap RGB from the SNES Jr. right off the VDP?

I don't even know why I ask about things I'll never bother with. Call me curious I suppose.

Yes, you can easily add RGB to a SNES 2/Jr :) see here for more info:-
http://gamesx.com/wiki/doku.php?id=av:snes2rgb
75ohm resistors in series seems to be the 'definitive' value, then just use a normal NTSC RGB cable (i.e. one with 220uF capacitors inside on R, G & B)

Offline RGB32E

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Re: Why?
« Reply #8 on: January 25, 2009, 01:17:17 am »
Yes, you can easily add RGB to a SNES 2/Jr :) see here for more info:-
http://gamesx.com/wiki/doku.php?id=av:snes2rgb
75ohm resistors in series seems to be the 'definitive' value, then just use a normal NTSC RGB cable (i.e. one with 220uF capacitors inside on R, G & B)
So wait, there seems to be conflicting info between the wiki and the old gamesx page on adding RGB to the SNES2.  Is the amp shown in the old page unnecessary for both NTSC and PAL SNES2 systems?  If the amp isn't necessary, I'll be modding mine today!  :o

Furthermore, if the amp shouldn't be used, why was it mentioned?

Online Link83

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Re: Why?
« Reply #9 on: January 25, 2009, 02:22:32 am »
Yep that amp is totally wrong im afraid - I think Kevin Horton who wrote the original mod thought that the video chip used in the SNES Jr/2 was the same as the one in the original SNES console - it isnt.

His mod seems to be based on the idea of 'copying' the SMT components that were used on the RGB lines in the original SNES console to 'restore' what was missing in the SNES Jr/2. His idea was great except for the fact they dont use the same video chip!

The original SNES used a 'BA6592' or 'S-ENC' video encoder chip which doesnt amplify the RGB in any way. The RGB only goes into the video chip so it can be encoded into S-Video and Composite. SMT components were then used to amplify the RGB signal direct from the SNES's PPU2 (Picture Processing Unit) to the MultiAV output.

The SNES Jr/2 (and the very last revision of the original SNES) used the 'S-RGB' or 'S-RGB A' video chip which does amplify and output RGB. The new video chip was obviously designed to help cut down on the amount of SMT video components that were used in the original SNES.

The SNES Jr S-Video mod page from the main page is also totally wrong aswell!

Without trying to be mean to Kevin Horton I think both pages should probably be removed from the main GamesX page to prevent any more confusion. The pages arent exactly easy to understand anyway...

<EDIT> I guessed those pages were wrong a few months ago after looking at a PAL SNES that also used the 'S-RGB' chip, but I still didnt know what the actual components should be as the PAL SNES has different video lines to the NTSC SNES (Due to different components being used in the video cables). I then found quite a few datasheets for the ROHM video chips used in the SNES and N64 which confirmed my suspicions - I even made a thread about them but didnt even get a single reply  :'(

Later, after googling around for some SNES motherboard pictures I actually came across this Spanish page that confirmed what I had thought and gives a good guide on how to add RGB and S-Video to a SNES Jr/2:-

http://translate.google.co.uk/translate?hl=en&sl=es&u=http://www.retrogaming.com.ar/forum/viewtopic.php%3Ff%3D4%26t%3D2652&sa=X&oi=translate&resnum=3&ct=result&prev=/search%3Fq%3DSNS-CPU-RGB-01%26hl%3Den%26safe%3Doff

The author even says "For obvious reasons I suppose that changing GamesX.com really does not work" I assume he means because he is Spanish?

I would have updated/added pages to the Wiki for SNES Jr/2 S-Video and RGB but the SNES Jr/2 was not released here in Europe and I could not easily acquire one, so there wasnt any way for me to confirm these mods worked - even though im 99% sure they do.
« Last Edit: January 25, 2009, 03:05:50 am by Link83 »

Offline Lawrence

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Re: Why?
« Reply #10 on: January 25, 2009, 09:00:41 am »
Just FYI, the SNESjr mod was my work, not K.Horton's, and you're right - I just copied the old system onto the new one.

I'm confused by the complaints that it doesn't work hwoever, it works flawlessly on mine.  What problems are you guys seeing?

NOTE: I've updated the mainpage link to the wiki page.
« Last Edit: January 25, 2009, 09:07:29 am by Lawrence »

Online Link83

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Re: Why?
« Reply #11 on: January 25, 2009, 11:59:48 am »
Sorry Lawrence - I hope I didnt offend you at all, I thought it was Kevin Hortons work as his name was mentioned at the top of the page.

I am sure both your mods work (I cant actually test them myself) its just that about 90% of the components are not actually needed/neccessary with the new 'S-RGB' video chip. I thought the complicated nature of the mods may have put a few people off attempting to add RGB/S-Video to a SNES Jr/2 when it is actually not all that hard - a few resistors and capacitors is all that is needed.

I hope you understood what I meant and wasnt offended when I said they 'arent exactly easy to understand' - the diagram here for instance still has me abit bewildered!:-
http://www.gamesx.com/rgbadd/snes2svid.htm

I hope you understand what I meant and didnt take it personally  :)
« Last Edit: January 25, 2009, 12:11:42 pm by Link83 »

Offline Lawrence

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Re: Why?
« Reply #12 on: January 25, 2009, 06:21:17 pm »
No offense taken.  Those diagrams mystify me now, but when I drew them they made total sense.  The images are shit too, really.  When I mapped it all out and hooked it all up, I was surprised it worked so well, and since I didn't really understand WHY, I just kinda left it.

If memory serves, hooking the RGB lines up directly results in a very washed out image, similar to tapping RGB directly from a PC Engine.  Hence the need for additional components...

Offline RGB32E

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Re: Why?
« Reply #13 on: January 29, 2009, 02:31:27 am »
Well, I performed the mod this past weekend, and it works fine.  I connected the RGBS to the appropriate pins with series 75 ohm resistors for RGB (and caps in the cable like normal).  The one thing that I noticed is that there is a little bit more noise.  I noticed this when playing Super Mario World - turn the game on, on the title screen when mario jumps on Yoshi, I noticed a little bit of a ghost image to the right... I'm wondering if this has something to do with the sync signal?  I was thinking about trying to run the sync signal through a 220uf electrolytic to see if that goes away.  I tried my old sytle snes (later model with no cart lock mech) and noticed the same thing, but was barely noticeable by comparison.  So, it might be in part my PVM-2030, but there's definitely a difference between the systems...  ???

Another thing I will be looking into is if the RGB goes to anywhere on the underside of the SNES PCB... that would make for easier soldering, shorter wire runs.  Maybe this offshoot thread should be opened to a new one... ("Adding RGB to the SNES 2 - Revisited")  :D
« Last Edit: January 29, 2009, 02:34:20 am by RGB32E »

Online Link83

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Re: Why?
« Reply #14 on: January 29, 2009, 06:20:18 am »
Glad it worked  ;D

Regarding the sync problem, another thing I have noticed in my research is that the sync for the SNESjr/2 is usually taken from the 'S-RGB' chips Sync input pin, but I believe there is also a Sync output pin aswell....

Now im not positive here, but having looked at alot of ROHM datasheets I believe the BA7232 is an almost direct successor to the BA6596 'S-RGB' video chip used in the SNES2, the main difference being that the BA7232 is a SOP20 package and the BA6596 a SOP24 package, as there are four extra pins on the BA6596 which are not connected/unused and are located between the Red, Green and Blue input and output pins, if you imagine these extra unused pins on the BA7232 both chips appear almost identical from what I have seen.

So having looked at the BA7232 datasheet here:-
http://www.datasheetarchive.com/pdf-datasheets/Datasheets-24/DSA-477788.pdf
You should find that Pin 18 on the 'S-RGB' is the Sync output pin (This isnt definite though and I could be totally wrong, so please see disclaimer below!*) Pin 18 is opposite the Sync input pin. According to the 'measurement circuit' diagram on page 4 you should use a 2K resistor to ground on the Sync line - although im unsure if this resistor is already present on the sync input on TV/Monitors? (The 75ohm resistors to ground shown on the RGB/Video lines etc are already in your TV/Monitor)
I have never had to use C-Sync before as all Scart TV's use the Sync from Composite Video.

...This is of course all assuming that the two chips are almost the same.

Alternatively, if anyone here has an original model NTSC SNES that has an 'SNS-CPU-RGB-01' or 'SNS-CPU-1CHIP-01' motherboard revision, these also use the 'S-RGB' video chip - so you should be able to follow the traces and components used on the Sync line. I have a PAL SNES with the 'S-RGB' chip, but thats no good as the PAL SNES uses different video components, and the Sync line is not even connected/used! (Its replaced by +12V for Scart auto-switching)

I'm surprised nobody was more interested in the SNES/N64 encoder datasheets when I posted my 'findings' weeks ago!:-
http://nfggames.com/forum2/index.php?topic=3525.0

P.S. I agree that it would be good to have another thread for these SNESjr/2 mods. Perhaps a mod can separate the relevent posts into a new thread?  ???

*Usual disclaimers apply  - this mod is totally untested, and should you try this I take no responsibilty for any damage/explosions it may cause!

<EDIT> Just wondered if your 'ghost image' could also be caused by interference if your using a poorly shielded cable? Oh and if your original SNES is one of the last models (You mentioned its a later model with no cart lock mech) do you know if it has one of the board revisions I mentioned above?  ;)

<SECOND EDIT> Just realised theres one other thing you could try - adding 22pf (or 47pf) capacitors to ground on each of the Red, Green and Blue lines after the 75ohm resistors - this should be relatively safe to try as Nintendo always seems to use these 'capacitors to ground' on all the video lines (R, G, B, Y, C & CVBS) for all their consoles. Lawrence even used them on the old SNES2 RGB mod and said these capacitors are "...just an interference filter, and you can probably leave it out entirely." but perhaps they are more important than I had first thought ??? I'd probably try adding these 'capacitors to ground' first and see if they make a difference before trying the alternative Sync mod I mentioned.
« Last Edit: February 01, 2009, 12:17:18 am by Link83 »

Offline RGB32E

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Re: Why?
« Reply #15 on: February 01, 2009, 04:41:29 am »
<EDIT> Just wondered if your 'ghost image' could also be caused by interference if your using a poorly shielded cable? Oh and if your original SNES is one of the last models (You mentioned its a later model with no cart lock mech) do you know if it has one of the board revisions I mentioned above?  ;)
I'm using an official Nintendo Gamecube Scart cable, but with the scart connector replaced with a DB25 and put in a different hood (for PVM2030).  I changed over to CSYNC quite a while ago (instead of composite video), but that uses a standard wire instead of a coax (think pin 3... CSYNC on NTSC, +12VDC on PAL)... but that shouldn't be a problem either...

<SECOND EDIT> Just realised theres one other thing you could try - adding 22pf (or 47pf) capacitors to ground on each of the Red, Green and Blue lines after the 75ohm resistors - this should be relatively safe to try as Nintendo always seems to use these 'capacitors to ground' on all the video lines (R, G, B, Y, C & CVBS) for all their consoles. Lawrence even used them on the old SNES2 RGB mod and said these capacitors are "...just an interference filter, and you can probably leave it out entirely." but perhaps they are more important than I had first thought ??? I'd probably try adding these 'capacitors to ground' first and see if they make a difference before trying the alternative Sync mod I mentioned.
I'll have to give the cap to ground a shot.  Any non-polarized caps should work?